Non-maximally entangled states: production, characterization and utilization

Andrew G. White, Daniel F. V. James, Philippe H. Eberhard, Paul G. Kwiat

Published 1999-08-27Version 1

Using a spontaneous-downconversion photon source, we produce true non-maximally entangled states, i.e., without the need for post-selection. The degree and phase of entanglement are readily tunable, and are characterized both by a standard analysis using coincidence minima, and by quantum state tomography of the two-photon state. Using the latter, we experimentally reconstruct the reduced density matrix for the polarization. Finally, we use these states to measure the Hardy fraction, obtaining a result that is $122 \sigma$ from any local-realistic result.